From @bbkr

[18​:54] <bbkr> rakudo​: / x​:/
[18​:54] <p6eval> rakudo 6ccdcd​: ( no output )

[18​:54] <bbkr> std​: / x​:/
[18​:54] <p6eval> std 32116​: OUTPUT«�[31m===�[0mSORRY!�[31m===�[0mâ�¤Unrecognized
regex metacharacter : (must be quoted to match literally) at /tmp/p4Hf1aN4K8
line 1​:â�¤------> �[32m/ x​:�[33mâ���[31m/�[0mâ�¤Check failedâ�¤FAILED 00​:01 116mâ�¤Â»

From @bbkr

On 2012.06​:

$ perl6 -e 'say "x​:" ~~ / x​:/'
q[x]

$ perl6 -e 'say "x​:" ~~ / x\​:/'
q[x​:]

Colon is used for http://perlcabal.org/syn/S05.html#Backtracking_control .

The RT System itself - Status changed from 'new' to 'open'

From @Mouq

This seems more like a STD bug than anything to do with Rakudo​:

00​:26 <Mouq> std​: / x​:/
00​:26 <camelia> std f9b7f55​: OUTPUT«===SORRY!===â�¤Unrecognized regex metacharacter : (must be quoted to
  match literally) at /tmp/v_cWVBkJqC line 1​:â�¤------> / x​:â��/â�¤Check failedâ�¤FAILED 00​:01
  136mâ�¤Â»
00​:26 <Mouq> std​: / x​: /
00​:26 <camelia> std f9b7f55​: OUTPUT«ok 00​:00 135mâ�¤Â»

On Mon Jul 02 09​:23​:09 2012, bbkr wrote​:

On 2012.06​:

$ perl6 -e 'say "x​:" ~~ / x​:/'
q[x]

$ perl6 -e 'say "x​:" ~~ / x\​:/'
q[x​:]

Colon is used for http://perlcabal.org/syn/S05.html#Backtracking_control .

From @jnthn

On Sat Feb 14 21​:28​:09 2015, Mouq wrote​:

This seems more like a STD bug than anything to do with Rakudo​:

00​:26 <Mouq> std​: / x​:/
00​:26 <camelia> std f9b7f55​: OUTPUT«===SORRY!===â�¤Unrecognized regex
metacharacter : (must be quoted to
match literally) at /tmp/v_cWVBkJqC line 1​:â�¤------> /
x​:â��/â�¤Check failedâ�¤FAILED 00​:01
136m�»
00​:26 <Mouq> std​: / x​: /
00​:26 <camelia> std f9b7f55​: OUTPUT«ok 00​:00 135mâ�¤Â»

On Mon Jul 02 09​:23​:09 2012, bbkr wrote​:

On 2012.06​:

$ perl6 -e 'say "x​:" ~~ / x​:/'
q[x]

$ perl6 -e 'say "x​:" ~~ / x\​:/'
q[x​:]

Colon is used for
http://perlcabal.org/syn/S05.html#Backtracking_control .

We discussed this a good bit on channel, and the conclusion was that it is indeed STD in the wrong​:

http://irclog.perlgeek.de/perl6/2015-07-20#i_10926978

However, we did end up tightening something up in Rakudo's regex grammar; that was ticketed as RT #​125648.

Added tests capturing the decision on this ticket to S05-metasyntax/regex.t.

@jnthn - Status changed from 'open' to 'resolved'